Delivery regulator for a fuel injection pump

Abstract

The invention relates to an internal combustion engine injection pump provided with a regulator unit comprising a mobile valving element on which there act an actuator, elastic means, and the back-pressure of the fuel discharged by the pump on delivery interruption, in order to improve the response characteristics of the regulator unit.

We claim: 
     
       1. A fuel injection pump comprising at least one pumping unit which feeds fuel to at least one injector associated with an internal combustion engine cylinder, a regulator unit for regulating the pumping unit displacement, characterized in that said regulator unit comprises a duct which connects a pump feed pipe to a pressure chamber of said pumping unit successively by way of a non-return valve in parallel with a passage of predetermined size and by way of valve means of which a valving element is moved into the closed state by an actuator against the action of elastic means, one face of said valving element being subjected to the pressure of the liquid existing in a duct portion between said valve means and said passage of predetermined size, said pressure acting on the valving element in the sense of moving it concurrently with the elastic means, and that portion of said duct between the non-return valve and the valve means has a volume many times greater than the pumping unit displacement. 
     
     
       2. An injection pump as claimed in claim 1, characterised in that said duct widens into an intermediate back-pressure chamber in a position corresponding to said valve means. 
     
     
       3. An injection pump as claimed in claim 1, characterised in that said valving element is in the form of a plunger. 
     
     
       4. An injection pump as claimed in claim 2, characterised in that said valve means is represented by a cylindrical plunger provided with an axial bore connected to said back-pressure chamber and opening into a sunken collar disposed in the central region of said cylindrical plunger, said cylindrical plunger being tightly slidable in a corresponding cylindrical housing and driven with reciprocating motion in order, when in its position closest to said intermediate back-pressure chamber, to interrupt the connection between said pumping unit pressure chamber and said back-pressure chamber. 
     
     
       5. A fuel injection pump comprising at least one pumping unit including at least one pumping element mounted for reciprocal movement relative to a pressure chamber, first duct means for delivering fuel into said pressure chamber, second duct means for delivering pressurized fuel from said pressure chamber to a delivery duct, third duct means for delivering fuel to said pressure chamber in parallel relationship to said first duct means, said third duct means including a restricted orifice and a movable valve disposed in serial relationship, said third duct means being defined in part by passage means in said movable valve for selectively maintaining fluid communication between said pressure chamber and a portion of said third duct means between said restricted orifice and said movable valve, actuator means for moving said movable valve means to a position closing off fluid communication through said passage means, means for biasing said movable valve in a direction opposite to the closing movement of said movable valve by said actuator means, and the force of fluid acting against said movable valve when the latter opens fluid communication through said passage means being in a direction additive to the force of said biasing means. 
     
     
       6. A fuel injection pump comprising at least one pumping unit including a fuel feed chamber, a pressure chamber and a pumping piston reciprocable in said pressure chamber, first duct means between said fuel feed chamber and said pressure chamber for delivering fuel into said pressure chamber, second duct means between said pressure chamber and at least one delivery duct for delivering pressurized fuel into said at least one delivery duct, third duct means between said fuel feed chamber and said pressure chamber in substantially parallel relationship to said first duct means, said third duct means comprising a restricted orifice and a movable valve means arranged in serial relationship and spaced for each oher by a portion of said third duct means, actuator means for moving said movable valve means between a position shutting off fluid communication between said pressure chamber and said portion of said third duct means and a position providing said fluid communication, and means for biasing said movable valve means in a direction opposite to the movement caused by said actuator means, whereby said restricted orifice causes pressure fluid in said portion of said third duct means between said restricted orifice and said movable valve means to act against said movable valve means in a drection additive to the force of said biasing means when said movable valve means provide said fluid communication between said pressure chamber and said portion of said third duct means. 
     
     
       7. A fuel injection pump as claimed in claim 6, wherein said portion of said third duct means has a volume many times greater than the delivery volume of said pumping pumping piston. 
     
     
       8. A fuel injection pump as claimed in claim 6, wherein said portion of said third duct means widens into an intermediate back-pressure chamber close to said movable valve means. 
     
     
       9. A fuel injection pump as claimed in claim 6, wherein said portion of said third duct means widens into an intermediate back-pressure chamber close to said movable valve means, and wherein said movable valve means comprise a substantially cylindrical plunger having an axial bore communicating with said back-pressure chamber and opening into a sunken collar of said plunger located at a position between opposite ends of said plunger, said plunger being tightly reciprocable in a corresponding substantially cylindrical housing between a position close to said intermediate back-pressure chamber in which fluid communication from said pressure chamber to said back-pressure chamber through said axial bore is shut off and a position farther away from said back-pressure chamber in which fluid communication between said pressure chamber and said back-pressure chamber through said axial bore is provided. 
     
     
       10. A fuel injection pump as claimed in claim 9, wherein said substantially cylindrical housing defines an enlarged annular chamber in a position substantially corresponding to the position assumed by said sunken collar when said plunger is in said position farther away from said back-pressure chamber, said enlarged annular chamber communicating with said pressure chamber and defining means for balancing lateral thrust on said cylindrical plunger by the pressure existing in said pressure chamber. 
     
     
       11. A fuel injection pump as claimed in claim 6, wherein said portion of said third duct widens into an intermediate back-pressure chamber close to said movable valve means, and wherein said biasing means are arranged in said intermediate back-pressure chamber. 
     
     
       12. A fuel injection pump as claimed in claim 6, wherein said actuator means is an electromagnet. 
     
     
       13. A fuel injection pump as claimed in claim 6, wherein said actuator means comprises a cam element rotatably driven by a step motor. 
     
     
       14. A fuel injection pump as claimed in claim 6, wherein said restricted orifice is a fixed orifice defined in said third duct means. 
     
     
       15. A fuel injection pump as claimed in claim 6, wherein said restricted orifice is an axial orifice defined in a check valve, said check valve being arranged in said third duct means such as to allow fluid communication in a direction between said feed chamber and said portion of said third duct means.